This invention relates to processes and apparatuses for the extraction and recovery of blowing agents from polymeric foams.
It is desirable to extract and recover blowing agents from polymeric foams to determine the amount of blowing agent that was present in the foam, reclaim the blowing agent and/or reclaim the polymer. It is especially important to recover blowing agents from scrap foams since emissions of blowing agents to the atmosphere may cause damage to the environment. Also, reuse of the blowing agents enhances the economics of the foam manufacturing process.
Apparatuses have been developed to recover and reclaim blowing agents from thermoplastic and thermoset foams during their manufacture to reduce loss of blowing agent. In these processes, air is passed over foam manufacturing lines and scrap foam recovery units to sweep away any excess blowing agents. The resultant air/blowing agent mixture is then separated.
U.S. Pat. No. 4,531,951 (Cellu Products Company) discloses a blowing agent recovery unit for recovering blowing agent from foam during production. This unit comprises an enclosed area surrounding the exit of the foam extruder. A fan or a blower sucks the stream of blowing agent in air out of the enclosed area and sends it to an activated carbon adsorption unit. A blowing agent-rich stream is sent from the carbon adsorption unit to a condenser. Water is condensed out of the stream at the condenser. The blowing agent-rich stream is then sent to a compressor. This stream is then compressed and the blowing agent is thereby liquefied. The blowing agent is then passed through a pressurized vessel and the blowing agent settles to the bottom of this vessel and is removed via a valve at the bottom of the vessel.
U.S. Pat. No. 4,531,950 (Cellu Products Company) discloses a similar blowing agent recovery unit to the unit disclosed in the above-mentioned patent which also includes a scrap foam recovery unit. This unit grinds foam into small particles and pneumatically conveys the resultant particles and air-fluorocarbon mixture to a cyclone separator. Some of the air-fluorocarbon mixture obtained is then recycled for pneumatic conveying and some of it is sent to the main blowing agent recovery unit for separation of the air and the blowing agent.
The present invention is suitable for the process described in U.S. Pat. No. 4,976,862 (Du Pont Canada Inc.), the contents of which are incorporated herein by reference. The process described in the aforementioned patent comprises breaking up polymeric foam in a liquid medium to obtain a solid phase of polymeric fragments and a liquid phase of the blowing agent and liquid medium. The solid phase is then separated from the liquid phase. Optionally, in the liquid phase, the blowing agent may be separated from the liquid medium by distillation or decantation.